Optical measuring arrangement for recording distances

Abstract

Optical measuring arrangement for recording a distance between a first component and a second component by measuring the length of at least one measurement path, wherein the measurement path is spanned between firstly at least two facets that form a measuring head and are indirectly or directly connected or connectable to the first component and secondly a measurement target that is arranged in the measurement path, indirectly or directly connected or connectable to the second component and configured to steer a measurement beam (105) in the measurement path (101) back and forth between the facets, wherein the second facet (103) is formed as a reflective facet (103) and whereby a centre of curvature of one of the facets (102, 103) of the measuring head is located on the measurement target or at a distance of at most 20% of the distance between the facet and the measurement target (104).

Description

[0001] Optical measuring arrangement for recording distances

[0002] The present application claims the priority of German patent application 10 2024 206 889.6 of 22 July 2024. The entire disclosure of that patent application is incorporated by reference in the present application.

[0003] The invention relates to an optical measuring arrangement for recording a distance between a first component and a second component by measuring the length of at least one measurement path, wherein the measurement path is spanned between firstly at least two facets that form a measuring head and are indirectly or directly connected or connectable to the first component and secondly a measurement target that is arranged in the measurement path, indirectly or directly connected or connectable to the second component and configured to steer a measurement beam in the measurement path back and forth between the facets, wherein the second facet is formed as a reflective facet. The invention also relates to a projection exposure apparatus, a lithography apparatus, an inspection apparatus and a coordinate measuring machine.

[0004] Projection exposure apparatuses are used for producing extremely fine structures, in particular on semiconductor components or other microstructured component parts. The operating principle of said apparatuses is based on the production of very fine structures down to the nanometre range by way of generally reducing imaging of structures on a mask, a so-called reticle, on an element to be structured, a so- called wafer, that is provided with photosensitive material. The minimum dimensions of the structures produced are directly dependent on the wavelength of the light used. Said light is shaped for the optimum illumination of the reticle in an illumination optics unit. Recently, light sources having an emission wavelength of the order of a few nanometres, for example between 1 nm and 120 nm, in particular in the region of 13.5 nm, have increasingly been used. The described wavelength range is also referred to as the EUV range.

[0005] Apart from with the use of systems which operate in the EUV range, the microstruc- tured component parts are also produced using commercially established DUV systems, which have a wavelength of between 100 nm and 400 nm, in particular 193 nm. With the requirement to be able to produce smaller and smaller structures, the requirements in respect of optical correction in the systems have likewise increased further. Throughput is increased to increase efficiency with each new generation of projection exposure apparatuses in the EUV range or DUV range.

[0006] During operation of microlithographic projection exposure apparatuses, in which mask and wafer are usually moved relative to one another in a scanning process, the positions of the mirrors, some of which are movable in all six degrees of freedom, have to be set and maintained with high accuracy in order to avoid or at least reduce aberrations and accompanying impairments of the imaging result or else displacements of the image.

[0007] Various approaches for measuring the position of the individual mirrors and also of the wafer or the wafer stage and the reticle or the reticle stage are known in the prior art. Interferometric measuring arrangements, optical encoders and frequencybased position measurement using an optical resonator are known in the field of optical measuring arrangements.

[0008] An optical measuring arrangement for frequency-based position and / or distance measurement is described in DE 10 2012 212 663 A1 , for example. The latter discloses a resonator in the form of a Fabry-Perot resonator with two resonator mirrors, of which the first resonator mirror is secured to a reference element in the form of a measurement frame fixedly connected to the housing of the projection lens of the projection exposure apparatus and the second resonator mirror (as "measurement target") is secured to a mirror to be measured with regard to the position thereof. The actual distance measuring equipment comprises a radiation source, which is tuneable with respect to its optical frequency and which creates input coupling radiation that passes through a beam splitter and is input coupled into the optical resonator. In that case, the radiation source is controlled by a coupling device in such a way that the optical frequency of the radiation source is tuned to the resonant frequency of the optical resonator and is thus coupled to said resonant frequency. Input coupling radiation output coupled via a beam splitter is analysed by means of an optical frequency measuring device which can comprise e.g. a frequency comb generator for highly accurate determination of the absolute frequency. If the position of the EUV mirror changes in the x-direction, then together with the distance between the resonator mirrors the resonant frequency of the optical resonator also changes and hence - owing to the coupling of the frequency of the tuneable radiation source to the resonant frequency of the resonator - the optical frequency of the input coupling radiation changes as well, which is in turn recorded directly by the frequency measuring device.

[0009] Moreover, WO 2019 / 223968 A1 and the German patent application filed under application number 102022210369.6 disclose various resonators for recording the position of a movable component.

[0010] Interferometers are also a widely used option as regards an optical measuring arrangement for recording a position and / or distance. The interferometer comprises a reference path and a measurement path, with the light from a light source being divided between the measurement path and the reference path by means of a beam splitter. In the measurement path, the light is directed at the measurement target in the form of a mirror and reflected back to the beam splitter from there. In the reference path, the reference light beam is reflected off a further reference mirror back to the beam splitter, where it is merged with the reflected measurement beam such that the measurement beam and reference beam interfere. Known types of interferometers include heterodyne and homodyne interferometers. For example, a heterodyne interferometer is described in US 4,784,489 A.

[0011] In order to be able to record relative positions or distances with a high accuracy and also over large distances, the optical measuring arrangement must be as insensitive as possible to tilts of the measurement target.

[0012] Thus, the problem addressed by the present invention is that of providing an optical measuring arrangement, a projection exposure apparatus, a lithography apparatus, an inspection apparatus and a coordinate measuring machine, which records the position and / or distance of a component over a large measurement range with a high accuracy. The problem concerning the optical measuring arrangement is solved by means of an optical measuring arrangement having the features of Claim 1 . The problem concerning the projection exposure apparatus is solved by means of a projection exposure apparatus having the features of Claim 17. The problem concerning the lithography apparatus is solved by means of a lithography apparatus having the features of Claim 18, the problem concerning the inspection apparatus is solved by means of an inspection apparatus having the features of Claim 19, and the problem concerning the coordinate measuring machine is solved by means of a coordinate measuring machine according to the features of Claim 20. Advantageous embodiments with expedient developments are specified in the dependent claims.

[0013] In this context, the optical measuring arrangement is characterized in particular in that a centre of curvature of one of the facets of the measuring head is located or arranged on the measurement target or at a distance of at most 20%, preferably at most 10% and particularly preferably at most 5% of the distance between the facet and the measurement target. This allows the provision of an optical measuring arrangement that is more insensitive to a tilt of the measurement target. The term "facet" is understood to mean a polished surface. The facets or some of the facets can be formed as mirrors. The measurement target is preferably also formed as a facet, in particular as a reflective facet or a reflective mirror. The reflective facet preferably has a reflectivity of at least 80%, preferably at least 90%, particularly preferably at least 95% and most preferably at least 99%. The measurement target preferably has a planar form.

[0014] In particular, it is preferable for the first facet to be formed as an input and output facet of the measurement path in order to input couple the measurement beam into the measurement path and output couple the measurement beam from the measurement path and for the second facet to be formed with such curvature that its centre of curvature is located or arranged on the measurement target or at a distance of at most 20%, preferably at most 10% and particularly preferably at most 5% of the distance between the second facet and the measurement target. The first facet is thus formed to be at least partially transmissive. This allows the beam axes of the incoming and outgoing light beam, i.e. of the measurement beam, to correspond, irrespective of a tilt of the measurement target. The second facet may be formed as an end facet of the measurement path.

[0015] Furthermore, it is preferable for the radius of curvature of the first facet to be chosen to be greater than the distance between the first facet and the measurement target and less than twice the distance between the first facet and the measurement target. By preference, the radius of curvature of the first facet is greater than 1 .2 times and smaller than 1 .7 times the distance between the first facet and the measurement target. Particularly preferably, the radius of curvature of the first facet is greater than 1 .4 times and smaller than 1 .6 times the distance between the first facet and the measurement target. Most preferably, the radius of curvature of the first facet is 1 .5 times the distance between the first facet and the measurement target.

[0016] It is also advantageous if a curvature of the measurement target is chosen such that a beam caustic of the measurement beam entering through the first facet in the direction of the measurement target corresponds to the beam caustic of the measurement beam leaving the measurement target in the direction of the first facet. Thus, the measurement target can be curved or planar (i.e. with infinite radius of curvature). If the measurement target is curved, then the first facet may be planar or curved. If the first facet is curved, then the measurement target may be curved or planar. At least one of measurement target and first facet is therefore preferably curved.

[0017] Furthermore, it is advantageous if the surface of the first facet corresponds or approximately corresponds to the phase front of the measurement beam incident thereon, i.e. the phase front of the (leaving) measurement beam reflected off the measurement target and incident on the first facet. In particular, it is advantageous if the curvature of the surface of the first facet corresponds or approximately corresponds to the phase front, in particular to the curvature of said phase front, of the measurement beam reflected off the measurement target and incident on said first facet. Should the optical measuring arrangement take the form of an interferometer, it is advantageous if the first facet is formed as an exit surface of a beam splitter of the interferometer. Alternatively, the at least partially transmissive first facet can also be planar.

[0018] Moreover, it is advantageous if the measurement beam is designed to form a beam caustic with a beam waist along the measurement path, wherein the beam waist is formed between the measurement target and one of the facets.

[0019] Furthermore, it is advantageous if a beam caustic of the measurement beam entering through the first facet in the direction of the measurement target is chosen such that it corresponds or approximately corresponds to the beam caustic of the measurement beam leaving the measurement target in the direction of the first facet (i.e. of the measurement beam reflected off the measurement target in the direction of the first facet).

[0020] In an embodiment, it is preferable for the optical measuring arrangement to take the form of an interferometer, in particular a heterodyne interferometer, should a reference path and a beam splitter be additionally present. The beam splitter is configured to divide a light beam emitted by a light source between the measurement path to form the measurement beam and the reference path to form the reference beam. The reference path preferably comprises an additional reference facet that is arranged such that the reference light beam steered into the reference path by the beam splitter is reflected back onto the beam splitter, and the beam splitter is configured to merge the measurement beam output coupled from the measurement path with the reference beam. The measurement target is preferably formed as a reflective facet, in particular as a measurement mirror. The measurement target preferably has a planar form. Alternatively, the measurement mirror formed as a measurement target can also be curved and the first facet, as input and output facet, can be planar.

[0021] In this context, it is particularly preferable for the at least partially transmissive first facet to have a transmission of more than 95%, preferably of more than 98% and particularly preferably of more than 99.5%. Furthermore, it is advantageous if the at least partially transmissive facet comprises an antireflective coating at least in some areas. The first at least partially transmissive facet is preferably formed as a surface of the beam splitter in this case. Furthermore, it is advantageous if the partially transmissive first facet is designed to form a stable virtual cavity with the second facet and the measurement target, in such a way that the beam caustic incident on the second facet from the measurement mirror corresponds or approximately corresponds to the beam caustic leaving the second facet.

[0022] Furthermore, it is advantageous if the measurement beam to be input coupled into the measurement path is configured such that its caustic corresponds to an eigenmode of a virtual cavity formed by at least the first facet, the second facet and the measurement target.

[0023] Moreover, it is preferable for the surface of the reference facet, i.e. its curvature in particular, to be chosen such that it corresponds or approximately corresponds to the phase front, in particular to the curvature of the phase front, of the reference light beam incident on the reference facet. The phase front of the incident reference light beam thus deviates from the surface by no more than 25%, preferably by 10% and most preferably by no more than 5% of the wavelength used in the reference light beam. The surface of the reference facet on which the reference beam is incident is therefore preferably matched to the curvature of the phase front of the reference light beam incident thereon. In particular, the surface of the reference facet is identical or almost identical to the curvature of the reference beam incident thereon. This allows the caustic of the reference light beam reflected off the reference facet to reproduce the caustic of the incident reference light beam.

[0024] In this context, it is particularly advantageous if the reference light beam to be input coupled into the reference path is configured such that its caustic corresponds to an eigenmode of a virtual resonator formed by at least the first facet, the second facet and the measurement mirror. In particular, the caustics of the reference light beam to be input coupled into the reference path and of the measurement beam to be input coupled into the measurement path correspond to one another and preferably correspond to an eigenmode of the resonator formed by at least the first facet, the second facet and the measurement mirror.

[0025] By preference, the reference facet and the first at least partially transmissive facet have the same form. In particular, both facets have at least approximately the same curvature. Optionally, the measurement beam in the measurement path and the reference light beam in the reference path may have deviating polarizations. In that case, the beam splitter is formed as a polarization beam splitter. In particular, the measurement beam and the reference light beam may be polarized orthogonally to each other.

[0026] In an alternative to that or in addition, it is advantageous if the reference path and the measurement path each comprise a quarter-wave plate, and the beam splitter is formed as a polarization beam splitter / 4.

[0027] Alternatively, it is advantageous if the optical measuring arrangement is formed as an optical encoder, and if the measurement target is formed as a grating.

[0028] In a further alternative embodiment, it is preferable for the optical measuring arrangement to be formed as a measuring arrangement for frequency-based position and / or distance measurement. In that case, the measurement path preferably comprises an optical resonator in which a standing wave is formed. The optical resonator comprising at least the first facet, the second facet and the measurement target preferably has a finesse of at least 10, preferably at least 100, very particularly preferably at least 500. In that case, the measurement target is preferably also formed as a reflective facet, in particular as a measurement mirror and preferably as a planar measurement mirror. In comparison with the embodiment of the measuring arrangement as an interferometer, the first facet has a lower transmissivity. The reflectivity of the first facet is more than 95%, preferably more than 98% and very particularly preferably more than 99.5% in the present case. The optical measuring arrangement comprises an evaluation unit configured to record a change in distance by recording a change in a resonant frequency or in a parameter of the optical resonator associated with the resonant frequency. The optical measuring arrangement preferably comprises a frequency shifter and a control loop (preferably a Pound- Drever-Hall control loop), which is configured to adjust the frequency of a light beam emitted by the light source to a resonant frequency of the optical resonator. Alternatively, the light source can be formed tuneable, and the frequency of the tuneable light source can be adjusted to a resonant frequency of the optical resonator. To improve accuracy, it is advantageous if at least one third reflective facet is present in the measurement path and configured to reflect the measurement beam reflected off a starting point on the measurement target towards the third facet back to or approximately back to this starting point on the measurement target, i.e. the measurement beam is reflected back onto itself with an angular deviation of no more than 500 prad. In other words, at least one third folding facet is present. The third facet may be arranged on a common mount with at least one of the other facets or with all facets. In particular, the reflective second facet and the third reflective facet may be arranged adjacent to each other. The facets may be symmetrical or asymmetrical. The first facet may be arranged between the second facet and the third facet. The facets may also be arranged on top of each other.

[0029] Moreover, in one embodiment, it is preferable for the second reflective facet to be configured to steer the measurement beam from one measurement point to another measurement point on the measurement target when passing over the measurement path, wherein the measurement points are each spaced apart from the centre of curvature of the second facet and preferably point-symmetrical with respect to the centre of curvature of the second facet. Furthermore, it is advantageous if the distance between the centre of curvature of the second facet and the measurement points is greater than 0.5 mm, preferably greater than 1 mm and particularly preferably greater than 2 mm. In particular, it is preferable for the measurement beam to be steered multiple times from one of the measurement points to the respective other measurement point via the second facet.

[0030] Furthermore, as regards the formation of a stable real or virtual resonator, it is advantageous if the third reflective facet is curved and if the radius of curvature is greater than the distance d between the third facet and the measurement target and less than twice the distance between the first facet and the measurement target. By preference, the radius of curvature of the third facet is greater than 1 .2 times and smaller than 1 .7 times the distance between the third facet and the measurement target. Particularly preferably, the radius of curvature of the third facet is greater than 1 .4 times and smaller than 1 .6 times the distance between the third facet and the measurement target. Most preferably, the radius of curvature of the third facet is 1 .5 times the distance between the first facet and the measurement target. In an advantageous design, the first facet may be planar. To form a stable real or virtual resonator, the third reflective facet may also be curved.

[0031] By preference, the second facet is formed with such curvature that its centre of curvature is arranged on the measurement target or at a distance of at most 20%, preferably at most 10% and particularly preferably at most 5% of the distance between the further facet and the measurement target.

[0032] In addition, it is advantageous if the second facet and the third facet are configured such that the measurement radiation after entering the measurement path is incident on the third facet after 2n+2 reflections off the measurement target and 2n+1 reflections off the second facet, where n is a non-negative number. The optical measuring arrangement is configured such that each pass of the measurement path contains a total of 4n+4 reflections off the measurement target.

[0033] Furthermore, it is advantageous if the first facet and the third facet are arranged such that the distance b between the entry point of the measurement radiation into the measurement path on the first facet and a retroreflection point on the third facet corresponds to b=N*a or, at most, a deviation of 10% from b=N*a, where N is the number of reflections in the measurement path over a passage and a is the distance between the centre of curvature of the first facet and a measurement point on the measurement target. The offset of the entry point from the retroreflection point on the third facet in the plane defined by the entry point and the measurement point is b=N*a.

[0034] Moreover, to increase the measurement accuracy, it is advantageous if a further facet is present and configured to steer the measurement beam from one of the measurement points on the measurement target to the other measurement point on the measurement target.

[0035] In this context, it is advantageous if the centre of curvature of the at least one further reflective facet corresponds or approximately corresponds to the centre of curvature of the second reflective facet.

[0036] In order to be able to further increase the number of further facets and hence increase the accuracy when recording the distance, it is advantageous if at least one of the further facets forms a common surface with the second facet. At least one of the further facets and the second facet preferably have a monolithic embodiment.

[0037] The at least one further facet may have the same curvature properties as the second reflective facet. By preference, the at least one further facet is formed with such curvature that its centre of curvature is arranged on the measurement target or at a distance of at most 20%, preferably at most 10% and particularly preferably at most 5% of the distance between the further facet and the measurement target.

[0038] It is furthermore preferable for the third facet to be aligned normally with respect to the measurement beam of the measurement path incident on the third facet (at a retroreflection point) or with a deviation of less than 500 prad. In an alternative to that or in addition, it is advantageous if the first facet is aligned normally or approximately to the measurement path in the entry point.

[0039] Furthermore, it is advantageous if a plurality of optical measuring arrangements are present and configured to record the position of the second component, in particular to record the position of the second component or individual points of the second component in 6 degrees of freedom, and / or to record a deformation of the second component.

[0040] The projection exposure apparatus is characterized in particular in that at least one optical measuring arrangement is present. The second component to be measured of the projection exposure apparatus may preferably be at least one or more optical elements or a supporting structure of the projection exposure apparatus. The first component may be formed as a reference object, in particular as a reference frame, in such a way that the at least one optical measuring arrangement is configured to record the distance between the first component and the second component. In particular, it is advantageous if the projection exposure apparatus comprises a plurality of optical measuring arrangements configured to record the position of the second component or individual points of the second component, in particular in multiple degrees of freedom, preferably in 6 degrees of freedom. In an alternative to that or in addition, the plurality of optical measuring arrangements may also be configured to record a deformation of a surface of the second component. By recording the distance of the optical elements relative to a reference by means of the plurality of opti- cal measuring arrangements, their position or pose or else a deformation of the optical surface may be recorded, and the position or deformation may be adjusted, preferably by means of actuators. This improves the image quality of the projection exposure apparatus. The advantages and embodiments mentioned in relation to the optical measuring arrangement are also applicable to the projection exposure apparatus comprising at least one optical measuring arrangement.

[0041] Furthermore, at least one optical measuring arrangement according to the invention may also be used in a projection lens, in particular in a projection lens of a projection exposure apparatus, for determining the position and / or distance of a movable or immovable component of the projection lens. In particular, it is advantageous if the projection lens comprises a plurality of optical measuring arrangements configured to record the position of the second component or individual points of the component, in particular in multiple degrees of freedom, preferably in 6 degrees of freedom. In an alternative to that or in addition, the plurality of optical measuring arrangements may also be configured to record a deformation of a surface of the component.

[0042] The invention may also be used in an illumination apparatus, in particular in an illumination apparatus for a projection exposure apparatus. The illumination apparatus preferably comprises at least one optical measuring arrangement. The at least one optical measuring arrangement, in particular its measurement target, is connected or connectable indirectly or directly to the second component to be measured. The second component may in particular be an optical element or a supporting structure. The illumination apparatus of a lithography apparatus comprises in particular a light source configured to create light in an EUV or DUV wavelength range and a plurality of optical elements configured to deflect the light created by the light source and input couple said light into the projection exposure apparatus. In particular, it is advantageous if the illumination apparatus comprises a plurality of optical measuring arrangements configured to record the position of the second component or individual points of the second component, in particular in multiple degrees of freedom, preferably in 6 degrees of freedom. In an alternative to that or in addition, the plurality of optical measuring arrangements may also be configured to record a deformation of a surface of the second component. In this context, the advantages and embodiments mentioned in relation to the optical measuring arrangement also apply to the illumination apparatus comprising at least one optical measuring arrangement.

[0043] The lithography apparatus is characterized in particular in that at least one optical measuring arrangement is present. The second component to be measured of the lithography apparatus may preferably be at least one or more optical elements, supporting structures, stages or masks of the lithography apparatus. In particular, it is advantageous if the lithography apparatus comprises a plurality of optical measuring arrangements configured to record the position of the second component or individual points of the second component, in particular in multiple degrees of freedom, preferably in 6 degrees of freedom. In an alternative to that or in addition, the plurality of optical measuring arrangements may also be configured to record a deformation of a surface of the second component. By recording the distance of the second components, for example formed as optical elements, by means of the at least one measuring arrangement, preferably by a plurality of optical measuring arrangements, their relative position or pose or else a deformation of the optical surface may be recorded vis-a-vis a first component, i.e. a reference object, and the position or deformation may be adjusted, preferably by means of actuators. The advantages and embodiments mentioned in relation to the optical measuring arrangement are also applicable to the lithography apparatus comprising at least one optical measuring arrangement.

[0044] The inspection apparatus according to the invention for checking an optical element or a wafer, a wafer stage, a reticle or a reticle stage comprises at least one optical measuring arrangement according to the invention. The optical measuring arrangement is configured to record the relative position or the distance of a component, i.e. of for example an optical element, a wafer, a wafer stage, a reticle or a reticle stage. In this case, an evaluation unit is preferably present, which compares the recorded positions or distances, in particular of structures of the component, with predetermined distances or positions of the structures or components and, in the event of a deviation by a predetermined limit value, causes measures to be taken. To this end, the at least one optical measuring arrangement is connected or connectable indirectly or directly to the component to be measured. In this context, the advantages and embodiments mentioned in relation to the optical measuring arrangement also apply to the inspection apparatus comprising at least one optical measuring arrangement. An example of such an inspection apparatus for the inspection of masks or wafers (without the optical measuring arrangement according to the invention) is known from document DE 10 2012 205 181 A1 , the entire content of which is incorporated by reference in the present application.

[0045] The invention may also be used in a measuring machine for recording a position, geometry or shape of a component. In that case, the measuring machine comprises at least one optical measuring arrangement according to the invention. By preference, the at least one optical measuring arrangement is indirectly or directly connected to the component. The measuring machine may be used in particular in the context of production technology or industrial metrology in mechanical engineering, for example in the automotive industry or aeronautical engineering. To this end, the at least one optical measuring arrangement is connected or connectable indirectly or directly to the component to be measured. In this context, the advantages and embodiments mentioned in relation to the optical measuring arrangement also apply to the measuring machine comprising at least one optical measuring arrangement.

[0046] The coordinate measuring machine according to the invention comprises at least one optical measuring arrangement according to the invention. Coordinate measuring machines are used for inspecting or measuring components, wherein the component is usually sensed, and distances or positions are determined using the sensing results. For this purpose, an optical system as well as a movable frame structure and / or a highly accurate positioning system are present, which support the component or object to be inspected. The optical measuring arrangement is preferably connected indirectly or directly to this movable component, i.e. frame structure or positioning system. The position or distance of the movable component can be determined by means of the at least one optical measuring arrangement, whereby the sensing of the object can be controlled. Moreover, the optical measuring arrangement may also be used to record the distance or position of the component itself and thus inspect the latter. In this context, the advantages and embodiments mentioned in relation to the optical measuring arrangement also apply to the coordinate measuring machine comprising at least one optical measuring arrangement. An ex- ample of such a coordinate measuring machine (without the optical measuring arrangement according to the invention) is known from document DE 10 2019 213 794 A1 , the entire content of which is incorporated by reference in the present application.

[0047] The optical measuring arrangement according to the invention may also be used in a measuring machine. The measuring machine comprises at least one optical measuring arrangement according to the invention. By preference, the at least one optical measuring arrangement is indirectly or directly connected to the component. The measuring machine may be used in particular in the context of production technology or industrial metrology in mechanical engineering, for example in the automotive industry or aeronautical engineering. To this end, the at least one optical measuring arrangement is connected or connectable indirectly or directly to the component to be measured. In this context, the advantages and embodiments mentioned in relation to the optical measuring arrangement also apply to the measuring machine comprising at least one optical measuring arrangement.

[0048] Further features, properties and advantages of the present invention are described in more detail below on the basis of embodiment variants and with reference to the appended figures. In this respect, all the features described above and below are advantageous both individually and in any desired combination. The embodiment variants described below are merely examples which, however, do not limit the subject matter of the invention. In the figures:

[0049] Figure 1a shows a schematic illustration of a microlithographic projection exposure apparatus designed for operation in the EUV,

[0050] Figure 1 b shows a schematic illustration of a microlithographic projection exposure apparatus designed for operation in the DUV,

[0051] Figure 2 shows a schematic illustration of a first exemplary embodiment of an optical measuring arrangement in the form of an interferometer, Figure 3 shows a schematic illustration of a side view (a) and a top view (b) of a second exemplary embodiment of an optical measuring arrangement having a further facet,

[0052] Figure 4 shows a schematic illustration of a side view (a) and a top view (b) of a third exemplary embodiment of an optical measuring arrangement having two further facets,

[0053] Figure 5 shows a schematic illustration of a side view and a top view of a fourth exemplary embodiment of an optical measuring arrangement having three further facets,

[0054] Figure 6 shows schematic illustrations of facet arrangements of the exemplary embodiment according to Figure 3,

[0055] Figure 7 shows schematic illustrations of facet arrangements of the exemplary embodiment according to Figure 4, and

[0056] Figure 8 shows a schematic illustration of a facet arrangement of the exemplary embodiment according to Figure 5.

[0057] Figure 1a shows a schematic illustration of an exemplary projection exposure apparatus 600 which is designed for operation in the EUV and in which the present invention can be realized. However, the invention can also be used in other nanopositioning systems.

[0058] In accordance with Fig. 1a, an illumination device in a projection exposure apparatus 600 designed for EUV comprises a field facet mirror 603 and a pupil facet mirror 604. The light from a light source unit comprising a plasma light source 601 and a collector mirror 602 is steered to the field facet mirror 603. A first telescope mirror 605 and a second telescope mirror 606 are arranged downstream of the pupil facet mirror 604 in the light path. Arranged downstream in the light path is a deflection mirror 607, which steers the radiation incident thereon to an object field in the object plane of a projection lens comprising six mirrors 651 -656. At the location of the object field, a reflective structure-bearing mask 621 is arranged on a mask stage 620 and with the aid of the projection lens is imaged into an image plane, in which a substrate 661 coated with a light-sensitive layer (photoresist) is situated on a wafer stage 660.

[0059] The invention can likewise be used in a DUV apparatus, as illustrated in Figure 1 b. A DUV apparatus is set up in principle like the above-described EUV apparatus from Figure 1a, wherein mirrors and lens elements can be used as optical elements in a DUV apparatus and the light source of a DUV apparatus emits used radiation in a wavelength range of 100 nm to 400 nm.

[0060] The DUV lithography apparatus 700 illustrated in Figure 1 b has a DUV light source 701 . For example, an ArF excimer laser that emits radiation 702 in the DUV range at for example 193 nm may be provided as the DUV light source 701. A beam shaping and illumination system 703 guides the DUV radiation 702 onto a photomask 704. The photomask 704 is embodied as a transmissive optical element and can be arranged outside the systems 703. The photomask 704 has a structure which is imaged onto a wafer 706 or the like in a reduced fashion by means of the projection system 705. The projection system 705 comprises a plurality of lens elements 707 and / or mirrors 708 for imaging the photomask 704 onto the wafer 706. In this case, individual lens elements 707 and / or mirrors 708 of the projection system 705 can be arranged symmetrically with respect to the optical axis 709 of the projection system 705. It should be noted that the number of lens elements 707 and mirrors 708 of the DUV lithography apparatus 700 is not restricted to the number illustrated. A greater or lesser number of lens elements 707 and / or mirrors 708 may also be provided. In particular, the beam shaping and illumination system 703 of the DUV lithography apparatus 700 comprises a plurality of lens elements 707 and / or mirrors 708. Furthermore, the mirrors are generally curved on their front side for beam shaping purposes. An air gap 710 between the last lens element 707 and the wafer 706 can be replaced by a liquid medium having a refractive index of >1 . The liquid medium can be high-purity water, for example. Such a set-up is also referred to as immersion lithography and has an increased photolithographic resolution. Figure 2 shows a first exemplary embodiment of an optical measuring arrangement

[0061] 100 for recording the relative position and / or distance between a first component (not depicted in detail) and a movable or immovable second component by measuring the length of at least one measurement path 101. The measurement path 101 is spanned between firstly at least two facets 102, 103 that are indirectly or directly connected or connectable to the first component and secondly a measurement target 104 that is arranged in the measurement path 101 , indirectly or directly connected or connectable to the second component and configured to steer a measurement beam 105 in the measurement path 101 back and forth between the facets 102, 103. The first facet 102 is preferably formed at least partially transmissive, and the second facet 103 is formed as a reflective facet. A centre of curvature 115 of one of the facets 102, 103, in particular of the second facet, is arranged on the measurement target 104 or at a distance of at most 20%, preferably at most 10% and particularly preferably at most 5% of the distance between the facet 102, 103 and the measurement target 104. This allows the provision of an optical measuring arrangement 100 that is more insensitive to a tilt of the measurement target 101. For example, the first component may be a reference frame or a supporting structure, while the second component may be an optical element, for example.

[0062] The optical measuring arrangement 100 shown in Figure 2 is in the form of an interferometer, in particular a heterodyne interferometer. The optical measuring arrangement 100 thus additionally comprises a reference path 110 and a beam splitter 108. The beam splitter 108 is configured to divide a light beam emitted by a light source (not depicted in detail here) between the measurement path 101 to form a measurement beam 105 and the reference path 110 to form a reference light beam 109, and to merge the measurement beam 105 output coupled from the measurement path

[0063] 101 with the reference light beam 109. The measurement target 104 is preferably formed as a reflective facet, in particular as a measurement mirror and preferably as a planar measurement mirror. Together with the measurement target 104, the first at least partially transmissive facet 102 and the second facet 103 form an open cavity in which the measurement beam 105 propagates as a light wave. Furthermore, the at least partially transmissive first facet 102 is formed as a surface of the beam splitter 108 or arranged on said beam splitter. The facets 102, 103 are formed at least as polished surfaces but may also be formed as mirrors. The measurement target 104 and the reflective second facet 103 preferably have a reflectivity of at least 95%, preferably at least 98%, particularly preferably at least 99% and most preferably at least 99.5%. In the present case, the centre of curvature 115 of the second facet 103 is arranged on the measurement target or at a distance of at most 20%, preferably at most 10% and particularly preferably at most 5% of the distance between the second facet 103 and the measurement target 104. This allows the beam axes of the incoming and outgoing measurement beam 105 to correspond, irrespective of a tilt of the measurement target 104.

[0064] In the exemplary embodiment according to Figure 2, the second facet 103 is formed as an end facet of the measurement path 101 . The first facet 102 is formed as an at least partially transmissive input and output facet of the measurement path 101 for input coupling the measurement beam 105 into the measurement path 101 and for output coupling the measurement beam 105 from the measurement path 101. A curvature of the phase front 106 of the measurement beam 105 entering through the at least partially transmissive first facet 102 in the direction of the measurement target 104 is chosen such that it corresponds or approximately corresponds to the curvature of the phase front 106 of the measurement beam 105 leaving the measurement target 104 in the direction of the first facet 102 at the same point (i.e. at the same location). The first facet 102 is preferably formed, in particular curved, such that it corresponds or approximately corresponds to the phase front 106 of the measurement beam 105 incident thereon, i.e. deviates at most by 10%, preferably 5%, particularly preferably 3% from the used wavelength of the measurement beam 105. The curvature of the surface of the first facet 102 is therefore identical to the curvature of the phase front 106 of the measurement beam 105 incident thereon. The radius of curvature of the at least partially transmissive first facet 102 is moreover preferably greater than the distance d between the first facet 102 and the measurement target 104 and less than twice the distance between the first facet 102 and the measurement target 104. To reduce cyclic errors, the first facet 102 may also have a convex lens element surface or be formed as a convex lens element. In another alternative embodiment, the first facet 102 may also be planar, while the measurement target 104 is curved. Moreover, the measurement target 104 and the first facet 102 may also be curved, or the measurement target is planar, and the first facet is curved. Furthermore, the at least partially transmissive first facet 102 may form a virtual cavity with the second facet 103 and the measurement target 104, in such a way that the beam caustic incident on the second facet 103 from the measurement target 104 corresponds at least approximately to the beam caustic leaving the second facet 103. The caustic of the measurement beam 105 to be input coupled into the measurement path 101 also preferably corresponds to an eigenmode of a virtual cavity formed by at least the first facet 102, the second facet 103 and the measurement target 104. The at least partially transmissive first facet 102 has a transmission of more than 95%, preferably of more than 98% and particularly preferably of more than 99.5%. Moreover, it may have an antireflective coating at least in some areas.

[0065] If the measurement target 104 is planar, the measurement beam 105 forms a beam path with a beam waist 118 along the measurement path 101 , wherein the beam waist 118 is formed between the measurement target 104 and one of the facets 102, 103.

[0066] The reference path 110 moreover additionally comprises a reference facet 111 arranged such that the reference light beam 109 steered from the beam splitter 108 into the reference path 110 is reflected back onto the beam splitter 108 and interferes there with the measurement beam 105 output coupled from the measurement path 101 . The curvature of the surface of the reference facet 11 1 is preferably chosen such that it corresponds or approximately corresponds to the curvature of the phase front 106 of the reference light beam 109 incident on the reference facet 111. The curvature of the phase front 106 of the incident reference light beam 109 thus deviates from the surface by no more than 10%, preferably by 5% and very preferably by no more than 3% of the wavelength used in the reference light beam 109. This allows the caustic of the reference light beam 109 reflected off the reference facet 111 to reproduce the caustic of the incident reference light beam 109.

[0067] The reference light beam 109 to be input coupled into the reference path 110 is preferably also configured such that its caustic corresponds to an eigenmode of a stable virtual cavity formed by at least the first facet 102, the second facet 103 and the measurement target 104. Consequently, in the present case, the caustic of the reference light beam 109 to be input coupled into the reference path 1 10 and the caustic of the measurement beam 105 to be input coupled into the measurement path 101 correspond at least approximately to one another and preferably each correspond to an eigenmode of the stable virtual cavity formed by at least the first facet 102, the second facet 103 and the measurement target 104.

[0068] The reference facet 111 and the first at least partially transmissive facet 102 are formed identically in the present case but may of course also differ from one another. In particular, both facets 111 , 102 have the same curvature at least approximately.

[0069] To divide the light beam emitted by the light source between a reference path 110 and a measurement path, the measurement beam 105 in the measurement path 101 and the reference light beam 109 in the reference path 1 10 have deviating polarizations. To this end, the reference path 110 and the measurement path 101 each comprise a quarter-wave plate / 4.

[0070] Alternatively, the optical measuring arrangement 100 shown in Figure 2 may also be formed as an optical measuring arrangement for frequency-based position measurement. In this case, deviating from the interferometer, the first facet 102 is formed as a highly reflective facet and part of an optical resonator which comprises at least the measurement target 104 and the second facet 103 and in which a standing wave is formed in the measurement path 101 . It is possible to omit the reference path 110. The frequency measurement is referenced by means of a further external cavity or a frequency comb. The optical measuring arrangement comprises an evaluation unit configured to record a change in distance by recording a change in a resonant frequency or in a parameter of the optical resonator associated with the resonant frequency. The optical measuring arrangement preferably comprises a frequency shifter (for example an electro-optic modulator, in particular an IQ modulator) and a control loop (preferably a Pound-Drever-Hall control loop), which is configured to adjust the frequency of a light beam emitted by a light source to a resonant frequency of the optical resonator. Alternatively, the light source can be formed tuneable, and the frequency of the tuneable light source can be adjusted to a resonant frequency of the optical resonator. An example of such an optical measuring arrangement is described in DE 10 2021 203 126 A1 , which is completely incorporated in the present case.

[0071] The exemplary embodiments illustrated in Figures 3 to 5 show optical measuring arrangements 100 which comprise a third facet 112 and optionally comprise further reflective facets 107, i.e. further folding facets. The third reflective facet 112 steers the measurement beam 105 originating from the measurement target 104 back to the measurement target 104. In this case, the third reflective facet 112 steers the measurement beam 105 reflected off a starting point 113 on the measurement target 104 to the third reflective facet 112 back or approximately back to this starting point 113 on the measurement target 104 again. Figure 3 shows an optical measuring arrangement 100 having exactly one third reflective facet 112. Figure 4 shows an optical measuring arrangement 100 in which the measurement path in addition to the third reflective facet 112 comprises an even further facet 107, which is configured to steer the measurement beam 105 from one measurement point 114a on the measurement target 104 to the other measurement point 114b on the measurement target 104. Figure 5 shows an optical measuring arrangement 100 whose measurement path 101 comprises two further reflective facets 107 in addition to the third reflective facet 112. However, the concept of the optical measuring arrangement 100 described presently may also be extended to any number of further reflective facets 107. The measurement beam 105 is steered from one of the measurement points 114a,b to the respective other measurement point 114b, a multiple times via the second facet 103.

[0072] The accuracy associated with recording the distance and / or position of the component is increased by the third facet 112 and each further reflective facet 107 since the measurement distance is passed over more frequently during the recording. The third facet 112 and / or the at least one further facet 107 may be arranged on a common mount 119 or frame with at least one of the other facets 102, 103 or with all facets 102, 103, 1 12 apart from the measurement target 104. In particular, the reflective second facet 103, the third reflective facet 112 and / or the further reflective facets 107 may be arranged adjacent to one another (Figures 6a, 6c, Figures 7a, b). The second facet 103 may be arranged between the first facet 102 and the third reflective facet 112 (Figure 6b). The facets 102, 103, 107, 112 may also be arranged on top of one another as desired. This is illustrated in Figures 6 to 8. Figure 6b) illustrates a symmetrical arrangement of the facets 102, 103, 112, while an asymmetrical arrangement of the facets 102, 103, 112 is shown in Figure 6c). The surfaces of the third facet 112 and / or the further facet 107 preferably lie at least approximately in a plane with the surface of the first facet 102. The third facet 112 is aligned normally to the measurement beam 105 incident on the third facet 112 at a retroreflection point 117 of the measurement path 101 or with a deviation of less than 500 prad. It is likewise advantageous if the first facet 102 is aligned normally to the measurement path 101 at its entry point 116.

[0073] The fact that the third facet 112 is curved can be gathered from Figure 3. To form a stable real optical resonator for recording the position and / or distance in frequencybased fashion or to form a stable virtual resonator for an interferometer, it is advantageous if the radius of curvature R of the third facet 112 is greater than the distance d between the further facet 112 and the measurement target 104 and less than twice the distance 2d between the further facet 112 and the measurement target 104. In particular, it is advantageous if the following applies to the radius of curva-

[0074] 3 ture R of the third facet R = - d ± x%, where x is less than 20%, preferably less than 15% and very particularly preferably less than 10%.

[0075] The measurement path 101 is designed such that the measurement beam 105 is incident on the measurement target 104 at at least two different measurement points 114a,b when passing over the measurement path 101 , said measurement points each being spaced apart from the centre of curvature 115 of the second facet 103. In particular, the measurement points 114a,b are point symmetrical with respect to the centre of curvature 115 of the second reflective facet 103. The distance between the centre of curvature 115 of the second facet 103 and the measurement points 114a,b is at least 0.5 mm, preferably at least 1 mm and particularly preferably at least 2 mm in this case.

[0076] The second reflective facet 103 and the third facet 112 are arranged such that the measurement beam 105 after entering the measurement path 101 is incident on the third reflective facet 112 after 2n+2 reflections off the measurement target 104 and 2n+1 reflections off the second reflective facet 103, where n is a non-negative num- ber. For example, this is illustrated in Figure 3. This relationship also applies to embodiments which additionally comprise even further reflective facets 107 should the second reflective facet 103 and the further reflective facets 107 form a common surface.

[0077] The first facet 102 and the third facet 112 are preferably arranged such that the distance b between the entry point 116 of the measurement beam 105 into the measurement path 101 on the first facet 102 and a retroreflection point 117 on the third facet 112 corresponds to b=N*a or, at most, a deviation of 10% from b=N*a, where N is the number of reflections in the measurement path 101 over one passage and a is the distance between the centre of curvature 1 15 of the second facet 103 and a measurement point 114a,b on the measurement target 104. The offset of the entry point 116 from the retroreflection point 117 on the third facet 112 in the plane defined by the entry point 116 and the measurement point 114a,b is b=N*a.

[0078] The exemplary embodiment according to Figure 4 differs in that the optical measuring arrangement 100 additionally comprises a further reflective facet 107, which is configured to steer the measurement beam 105 from one of the measurement points 114a on the measurement target 104 to the other measurement point 114b on the measurement target 104. Figure 7 illustrates possible arrangements of the first facet 102, the second facet 103, the third facet 112 and the further reflective facet 107. In this case, the second facet 103 and the at least one further facet 107 may form a common polished surface, as illustrated in Figure 7b). However, the facets 103, 107 may also be arranged separately from one another. By preference, the centre of curvature of the at least one further reflective facet 107 is located on the measurement target 104 or at a distance of at most 20%, preferably at most 10% and particularly preferably at most 5% of the distance between the further reflective facet 107 and the measurement target 104. The centre of curvature of the further reflective facet 107 at least approximately corresponds to the centre of curvature 115 of the second reflective facet 103.

[0079] The exemplary embodiment according to Figure 5 differs in that the optical measuring arrangement 100 comprises two further reflective facets 107. In this case, the facets 102, 103, 1 12 may be arranged as illustrated in Figure 8, for example. In particular, one or some of the further reflective facets 107 may form a common polished surface with the second facet 103.

[0080] The optical measuring arrangements 100 shown in Figures 2 to 8 may be formed as an interferometer or as an optical measuring arrangement 100 for frequency-based position and / or distance measurement. Should the optical measuring arrangement 100 be formed as an optical encoder, the measurement target 104 in the measurement path 101 is formed as a diffraction grating. If the optical measuring arrangement 100 is configured for frequency-based position and / or distance measurement, then the measurement path 101 comprises an optical resonator that is designed for the formation of a standing wave. In this case, the optical resonator is formed at least by the first facet 102, the second facet 103 and the measurement target 104 but may also comprise the third reflective facet 112 and further reflective facets 107. In comparison with the embodiment of the optical measuring arrangement 100 as an interferometer, the first facet 102 has a lower transmissivity. The reflectivity of the first facet 102 is more than 95%, preferably more than 98% and very particularly preferably more than 99.5% in the present case. If the optical measuring arrangement 100 is formed as an interferometer, then the first facet 102 is formed to be partially transmissive. To this end, the first facet 103 may also comprise an antireflec- tive coating. The measurement target 104 is formed as a reflective facet or as a (preferably planar) measurement mirror. The measurement path 101 may form a virtual resonator in which the measurement beam propagates as a wave.

[0081] LIST OF REFERENCE SIGNS

[0082] 100 Optical measuring arrangement

[0083] 101 Measurement path

[0084] 102 First facet

[0085] 103 Second facet

[0086] 104 Measurement target

[0087] 105 Measurement beam

[0088] 106 Phase front

[0089] 107 Further reflective facet

[0090] 108 Beam splitter

[0091] 109 Reference light beam

[0092] 110 Reference path

[0093] 111 Reference facet

[0094] 112 Third reflective facet

[0095] 113 Starting point (on the measurement target)

[0096] 114 Measurement point (on the measurement target)

[0097] 115 Centre of curvature (of the second facet)

[0098] 116 Entry point (measurement path)

[0099] 117 Retroreflection point (further facet)

[0100] 118 Beam waist

[0101] 119 Mount

[0102] 120 Quarter-wave plate / 4-

[0103] 121 Additional facet

[0104] 600 Projection exposure apparatus

[0105] 601 Plasma light source

[0106] 602 Collector mirror

[0107] 603 Field facet mirror

[0108] 604 Pupil facet mirror

[0109] 605 First telescopic mirror

[0110] 606 Second telescopic mirror

[0111] 607 Deflection mirror

[0112] 620 Mask stage

[0113] 621 Mask 651 Mirror (projection lens)

[0114] 652 Mirror (projection lens)

[0115] 653 Mirror (projection lens)

[0116] 654 Mirror (projection lens) 655 Mirror (projection lens)

[0117] 656 Mirror (projection lens)

[0118] 660 Wafer stage

[0119] 661 Coated substrate

[0120] 700 DUV lithography apparatus 701 DUV light source

[0121] 702 DUV radiation / beam path

[0122] 703 Beam shaping and illumination system (DUV)

[0123] 704 Photomask

[0124] 705 Projection system 706 Wafer

[0125] 707 Lens element

[0126] 708 Mirror

[0127] 709 Optical axis

Claims

CLAIMS1 . Optical measuring arrangement (100) for recording a distance between a first component and a second component by measuring the length of at least one measurement path (101 ), wherein the measurement path (101 ) is spanned between firstly at least two facets (102, 103) that form a measuring head and are indirectly or directly connected or connectable to the first component and secondly a measurement target (104) that is arranged in the measurement path (101 ), indirectly or directly connected or connectable to the second component and configured to steer a measurement beam (105) in the measurement path (101 ) back and forth between the facets, wherein the second facet (103) is formed as a reflective facet (103), characterized in that a centre of curvature of one of the facets (102, 103) of the measuring head is located on the measurement target (104) or at a distance of at most 20% of the distance between the facet (102, 103) and the measurement target (104).

2. Optical measuring arrangement (100) according to Claim 1 , characterized in that the first facet (102) is formed as an input and output facet of the measurement path (101 ) in order to input couple the measurement beam (105) into the measurement path (101 ) and output couple the measurement beam (105) from the measurement path (101 ) and in that the second facet (103) is formed with such curvature that its centre of curvature is located on the measurement target (104) or at a distance of at most 20% of the distance between the second facet (103) and the measurement target (104).

3. Optical measuring arrangement (100) according to either of Claims 1 and 2, characterized in that the radius of curvature of the first facet (102) is chosen to be greater than the distance between the first facet (102) and the measurement target (104) and less than twice the distance between the first facet (102) and the measurement target (104).

4. Optical measuring arrangement (100) according to any of Claims 1 to 3, characterized in that a curvature of the measurement target is chosen such that a beam caustic of the measurement beam entering through the first facet (102) in the direction of the measurement target (104) corresponds to the beam caustic of the measurement beam leaving the measurement target (104) in the direction of the first facet (102).

5. Optical measuring arrangement (100) according to any of Claims 1 to 4, characterized in that a beam caustic of the measurement beam (105) entering through the at least partially transmissive first facet (102) in the direction of the measurement target is chosen such that it corresponds or approximately corresponds to the beam caustic of the measurement beam (105) leaving the measurement target (104) in the direction of the first facet (102).

6. Optical measuring arrangement (100) according to any of Claims 1 to 5, characterized in that the surface of the first facet (102) corresponds or approximately corresponds to the phase front of the measurement beam (105) reflected off the measurement target and incident on the first facet (102).

7. Optical measuring arrangement (100) according to any of Claims 1 to 6, characterized in that additionally a reference path (110) is present, and in that a beam splitter (108) is present and configured to divide a light beam emitted by a light source between the measurement path (101 ) to form the measurement beam (105) and the reference path (110) to form a reference light beam (109), in that the reference path (110) additionally comprises a reference facet (111 ) that is arranged such that the reference light beam (109) steered into the reference path (110) by the beam splitter (108) is reflected back onto the beam splitter (108), and in that the beam splitter (108) is configured tomerge the measurement beam (105) output coupled from the measurement path (101 ) with the reference light beam (109).

8. Optical measuring arrangement (100) according to Claim 7, characterized in that the surface of the reference facet (111 ) corresponds or approximately corresponds to the phase front (106) of the reference light beam (109) incident on the reference facet (111 ).

9. Optical measuring arrangement (100) according to any of Claims 1 to 8, characterized in that the measurement path (101 ) takes the form of an optical resonator in which a standing wave is formed.

10. Optical measuring arrangement (100) according to any of Claims 1 to 9, characterized in that at least one third reflective facet (112) is present in the measurement path (101 ) and configured to reflect the measurement beam (105) reflected off a starting point (113) on the measurement target (104) towards the third reflective facet (112) back to or approximately back to this starting point (113) on the measurement target (104).

11. Optical measuring arrangement (100) according to Claim 9 or 10, characterized in that the second reflective facet (103) is configured to steer the measurement beam (105) from one measurement point (114a) on the measurement target (104) to another measurement point (114b) on the measurement target (104) when passing over the measurement path (101 ), wherein the measurement points (114a,b) are each spaced apart from the centre of curvature (115) of the second facet (103).

12. Optical measuring arrangement (100) according to Claim 11 , characterized in that the measurement beam (105) is steered multiple times from one of themeasurement points (114a,b) to the respective other measurement point (114b, a) via the second facet (103).

13. Optical measuring arrangement (100) according to any of Claims 10 to 12, characterized in that the third reflective facet (112) is curved, and in that the radius of curvature is greater than the distance between the third facet (112) and the measurement target (104) and less than twice the distance between the third facet (112) and the measurement target (104).

14. Optical measuring arrangement (100) according to any of Claims 10 to 13, characterized in that the second reflective facet (103) and the third facet (112) are arranged such that the measurement beam (105) after entering the measurement path (101 ) is incident on the third reflective facet (112) after 2n+2 reflections off the measurement target (104) and 2n+1 reflections off the second reflective facet (103), where n is a non-negative number.

15. Optical measuring arrangement (100) according to any of Claims 10 to 14, characterized in that the first facet (102) and the third reflective facet (112) are arranged such that the distance b between an entry point (116) of the measurement beam (105) into the measurement path (101 ) on the first facet (102) and a retroreflection point (116) on the third reflective facet (112) corresponds to b=N*a or, at most, a deviation of 10% from b=N*a, where N is the number of reflections in the measurement path (101 ) over a complete passage and a is the distance between the centre of curvature of the second facet (102) and a measurement point (114) on the measurement target (104).

16. Optical measuring arrangement (100) according to any of Claims 10 to 15, characterized in that a further facet (107) is present and configured to steer the measurement beam (105) from one of the measurement points (114a,b)on the measurement target (104) to the other measurement point (114b, a) on the measurement target (104).

17. Projection exposure apparatus (600, 700) having at least one optical measur- ing arrangement (100) according to any of Claims 1 to 16.

18. Lithography apparatus having at least one optical measuring arrangement (100) according to any of Claims 1 to 16.

19. Inspection apparatus for inspecting a shape, pose or geometry of an object, having at least one optical measuring arrangement (100) according to any of Claims 1 to 16.

20. Coordinate measuring machine having at least one optical measuring ar- rangement (100) according to any of Claims 1 to 16.

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